Good analysis overall....but one point to be made -
I think in the projected winners of Senate seats however there is a little too much reliance on the starting assumption that the vote at the next election will be the same as in 2007. The 2007 vote is the one that has been utilised but current polling shows the Coalition vote has dropped and The Greens vote has risen.
It is just as legitimate to make an assessment based on recent polling which could see more Greens elected in a half Senate election than predicted above and fewer Coalition candidates - e.g. on current polling it would be a close call as to whether a Green or Coalition candidate would be elected to the sixth seat in a half Senate election in NSW.
COMMENT: Entirely valid criticism, but I'd raise three points. First, the polls you quote are House polls not Senate polls. Second, Labor will be more interested in its own position than the Greens. Third, you could have made exactly the same point about any poll in 2007, except for the ones in the last two weeks before polling day. I expect to see the Coalition doing better next year than is indicated in current polls.
The best two-party preferred recorded by Labor in the last 60 years was 53.2% under Bob Hawke in 1983. It is entirely possible that Labor could do better than this in 2010, but at Australian Federal elections, it is very rare for a government to do better at it's first re-election than it did on coming to office. Perhaps Labor will do what some of its state brethren have done in recent years by increasing their majority at first re-election.
I am sure that any Labor decision making on whether to hold a double dissolution will not be based on assuming an increase in vote.

In three previous posts I have dealt with the constitutional bars on calling an early election (February 12 - An Early Federal Election?), the constitutional requirements to get a double dissolution trigger (May 14 - An Early Double Dissolution?),and the technical difficulties in using the doubl...